Driving means for rotary heat exchangers



March 4, 1969 D. J. 5. WARDALE 3,430,687

DRIVING MEANS FOR ROTARY HEAT EXCHANGERS Filed Aug. 1, 1967 Sheet L ofz INVENTOR. DAVID J. S. WARDALE A/MD. M

AGENT.

March 1969 D. J. 5. WARDALE 3,

DRIVING MEANS FOR ROTARY HEAT EXCHANGERS Filed Aug. 1, 1967 Sheet 2 of 2 INVENTOR. DAVID J. S. WARDALE A/MDW AGENT United States Patent O York Filed Aug. 1, 1967, Ser. No. 657,653 U.S. Cl. 165-8 Int. Cl. F2811 7/10; F28f 13/00, 21/04 8 Claims ABSTRACT OF THE DISCLOSURE A heat exchanger assembly comprising a rotary heat exchanger formed of a ceramic honeycomb structure driven by means of a ring gear coupled to the heat exchanger rim by a plurality of bow-like spring elements located between the inner surface of the ring gear and the rim of the heat exchanger. Each spring element is in the form of an elastic support member which is maintained in a curved form by means of a thin flexible web extending intermediate its ends, the support member having its convex surface in frictional engagement with the inner surface of the ring gear and the web being in tension and in frictional engagement with the outer rim of the ceramic honeycomb structure along a substantial portion of the web.

BACKGROUND OF THE INVENTION It has been discovered that certain low expansions ceramic materials, such as the ceramic materials disclosed in United States Patent 3,112,184, issued to R. Z. Hollenbach, function as particularly satisfactory matrix materials for regenerative heat exchangers. Such materials exhibit the advantages of high surface area, high maximum operating temperatures, low thermal conductivities and relatively high specific heats. Due to the fact that those ceramic materials most suitable for the construction of heat exchangers have very low thermal expansions, it has been difiicult to couple such heat exchangers to relatively high expansion metallic driving means in a manner so as to render the couplings effective throughout the temperature ranges under which such heat exchangers are required to operate. In the past, the problems resulting from disparities in thermal expansions have been met by such expedients as the formation of gear teeth directly in the ceramic heat exchanger rims or the coupling of such rims to a metallic ring gear by means of sinuated springs compressed between the ceramic rim and the inner surface of the surrounding metallic ring gear and forming a coupling therebetween by frictional engagement in the manner described in United States Patent 3,311,204, issued to M. C. S. Barnard. The former method is not entirely satisfactory since it is ditficult and expensive to cut gear teeth in ceramics, while the second method, due to the small areas of contact between the sinuated spring and the ceramic rim, generally requires a strong solid ceramic rim portion capable of withstanding the high pressures exerted by the spring at the points of contact with the rim.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a means for coupling a low expansion rotary heat exchanger to a surrounding ring gear of higher expansion in a manner so as to avoid the disadvantages associated with the above-mentioned coupling means of the prior art. This object is accomplished by the provision of a coupling means comprising a plurality of bow-like spring elements located within an annular space between the inner surface of a ring gear and the outer rim of a rotary 3,430,687 Patented Mar. 4, 1969 heat exchanger having a coefficient of thermal expansion differing from that of the ring gear. Each element is in the form of a spring-like support member which is generally concave in the direction of the heat exchanger rim and which has extending between its ends a web which 1s formed of a material which flexes more easily than the support member, such that when the composite spring element formed by the support member and the web is elastically compressed between the ring gear and the heat exchanger rim the web is maintained displaced by the heat exchanger rim in the direction of the support member, the ends of the support member are drawn closer together and, due to the resilience of the support member, the web is maintained in tension. The web is caused to conform to the heat exchanger rim along a substantial portion of the web, thereby distributing over a wide area the force required for frictional engagement between the web and the rim.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a side elevational view of a heat exchanger with driving means according to the invention.

FIGURE 2 is a perspective view of a spring element used in the driving means illustrated in FIGURE 1.

FIGURE 3 is a partial side elevational view of a driving means incorporating spring members of alternative design.

FIGURE 4 is a view similar to that of FIGURE 3, illustrating a further alternative spring element design.

FIGURE 5 is a side view of a further spring element design.

FIGURE 6 is a partial sectional view of a heat exchanger and driving means of alternate construction, taken in a plane through the axis of rotation of the heat exchanger.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIGURE 1 there is illustrated a heat exchanger assembly comprising an axial flow type rotary honeycomb heat exchanger 10 supported on a solid ceramic hub 11 and having an outer rim 12 in the form of a circular cylinder with its center at the center of the axis of rotation of the heat exchanger, such axis being designated by the numeral 14. Ring gear 16 surrounds the heat exchanger and has an inner surface in the form of a circular cylinder concentric with rim 12. Ring gear 16 is caused to rotate by means of driving gear 18, and rotation of the ring gear is transmitted to the heat exchanger by means of bow-like spring elements 20.

Each spring element 20 comprises spring-like support member 22 in the form of an arcuate plate which is concave in the direction of rim 12 and which supports a flexible web 24 suspended from its ends 26 and 2 8. In its relaxed position prior to its insertion between the ring gear and the heat exchanger, support member 22 is not subject to stress, and web 24 is not in tension; however, when the spring element is placed between the ring gear and the heat exchanger, support member 20 is bent so as to increase its curvature, preferably to a curvature greater than that of rim 12, and so as to permit web 24 to contact the heat exchanger rim along a substantial distance. Due to the tendency of the elastic support member to return to its original configuration, the Web is maintained in tension and is held tightly against the heat exchanger rim. while the central portion of the support member is pressed against the inner surface of the ring gear. Although the total force exerted on the heat exchanger rim by web 24 will 'be equal to the total force extered on the inner surface of the ring gear by member 22, due to the greater area of contact between the web and the heat exchanger rim the pressure per unit area exerted on the heat exchanger rim is substantially less than that exerted on the ring gear. Accordingly, there is no need for a strong solid ceramic rim, and the web may directly contact the honeycomb heat exchanger matrix.

Although the exact sizes and shapes of the respective components of the present assembly may be varied, the following description is provided as that of a preferred embodiment of the invention:

Heat exchanger body 10 may be formed in accordance with the teachings of the previously-mentioned Hollenbach patent and may have a cylindrical rim 28% inches in diameter located within a steel ring gear having a cylindrical inner surface with a diameter of 28% inches.

Hub 11 may be formed of a solid ceramic ring formed of the same ceramic material as that used in forming the heat exchanger honeycomb. Six spring elements may be employed, and each element may comprise a support member formed of stainless steel 0.120 inch thick, 2 /2 inches in width and 10 /2 inches long. The support members may have radii of curvatures of 14% inches prior to compression between the ring gear and the heat exchanger rim. The webs of the spring elements may extend from the ends of the support members and may be formed with widths of 2 /2 inches and thicknesses of 0.010 inch. When inserted between a ring gear and the heat exchanger rim approximately 6% inches of each web will be in contact with the heat exchanger rim. It has been calculated that when the ring gear and the heat exchanger have thermal coefficients of expansion of lZOXlO- per F. and -l 10- per F., respectively, and when the assembly is operated so that the heat exchanger is at about 900 F. and the ring gear at about 300 F. the spring element webs exert a pressure on the heat exchanger rim of approximately 9.5 p.s.i. a value well within the range of pressures which can be withstood by glass-ceramic heat exchangers.

As shown in FIGURES 3-5, the spring elements of the present invention may vary in shape. In FIGURE 3 there is shown a spring element 30 having a support member in the form of two straight leg portions 32 and 34. In FIGURE 4 there is shown a spring element having a support member 36 in the form of a straight elongated central portion 38 with two shorter straight leg portions 40 and 42 extending in directions transverse to the central portion. In FIGURE a spring element 44 is shown having a curved support member 46 and a web 48 in the form of a continuous thin metal band surrounding the support member.

Although frictional engagement is generally sufficient to prevent relative motion between the ring gear and the heat exchanger, the probability of such motion may be reduced, as illustrated in FIGURE 6, by the addition of lugs 50 and 52 to the outer surface of the support member 54, which lugs project into depressions in the inner surface of the ring gear 55, and spring element Web portions 56 may be located in a circumferential groove 58 extending around a central portion of the heat exchanger rim.

Inasmuch as the foregoing description has been provided solely as that of preferred embodiments of the present invention, it is intended that the scope of the invention be limited only by the scope of the appended claims, wherein the term ceramic is used to include both crystalline and vitreous materials, such a glass, and combinations of such materials, such as glass-ceramics.

What is claimed is:

1. A heat exchanger assembly comprising:

a heat exchanger,

a rim on said heat exchanger,

a ring gear surrounding said rim, said ring gear having a thermal coefiicient of expansion differing substantially from that of said exchanger rim and having an inner surface separated from said rim so as to form an annular space between said ring gear and said rim,

coupling means in said annular space for allowing said ring gear to drive said heat exchanger, and

means for rotating said ring gear,

wherein the improvement comprises:

said coupling means being a plurality of bow-like spring elements distributed about the circumference of said rim within said annular space, each said spring element comprising a support member having at least a portion in engagement with said inner surface of said ring gear and at least a portion which is generally concave in the direction of said rim of said heat exchanger, and

a flexible web extending across said concave portion of said support member and supported at its ends by said support member, said web being in frictional engagement withsaid rim of said heat exchanger and being maintained in tension thereagainst along a substantial portion of its length, whereby the total force between said web and said rim is sufiicient to permit said rim to be driven by frictional engagement between said rim and said web, while said force is distributed over a sufficient area to prevent damage to said rim.

2. An assembly according to claim 1 in which said heat exchanger comprises a ceramic honeycomb body.

3. An assembly according to claim 1 in which said web is more flexible than said support member.

4. An assembly according to claim 1 in which each said support member is an arcuate metallic plate having a radius of curvature less than that of said rim of said heat exchanger in the vicinity of said plate, and said web is a thin metallic sheet supported across said concave portion of said support member.

5. An assembly according to claim 1 in which said web is a portion of a continuous band of flexible material surrounding said support member and maintained in tension by the tendency of said ends of said support member to move away from one another.

6. An assembly according to claim 1 in which at least the portion of said web which is in contact with said rim contacts a circumferential groove portion formed in said rim, and the side of said support member in engagement with said inner surface of said ring gear is provided with at least one lug portion projecting into a depression in the inner surface of said ring gear.

7. An assembly according to claim 1 in which said support member and said web comprise stainless steel.

8. An assembly according to claim 1 in which said ring gear has a thermal coefl'icient of expansion higher than that of said heat exchanger.

References Cited UNITED STATES PATENTS 1/1967 Weaving et al -8 1/1968 Lanning 74--446 US. Cl. X.R. 165-10; 74446 

